The invention relates to securing an electrical motor to an electrical unit without the use of screws or bolts.
The invention is based on an electrical unit which has an electric motor and a machine that can be driven by it; the electric motor is connected to the machine. The machine can for instance be a piston pump for a slip-controlled vehicle brake system; that is, the electrical unit can be a piston pump assembly of a slip-controlled vehicle brake system. The machine can for instance also be a driven gear. For fastening the electric motor to a machine, it is known to use screws or bolts for fastening the electric motor to the machine. Another fastening possibility is disclosed by German patent disclosure DE 44 44 644 A1. The electric motor there has a cup-shaped housing, whose cylindrical edge protrudes from one face end into a circular groove in a housing of the machine and is secured with a clamping ring inserted into the groove. The clamping ring has a wedge-shaped annular cross section, and it is necessary that the groove in the housing of the machine be made with an outer flank that widens conically toward the bottom of the groove, so that the outer flank of the groove forms an undercut. It is therefore complicated to produce the groove. It is also necessary for the groove to be mounted concentrically to a shaft bearing in the housing of the machine, which because of the tolerance to be adhered to entails considerable effort and expense in production. Another factor of the known electrical unit is that an armature of the electric motor is supported in the housing of the machine, and not in the housing of the electric motor, and thus the function of the electric motor cannot be tested until after the electric motor has been fastened to the machine.
In the electrical unit of the invention as defined herinafter the electric motor has one or preferably more fastening elements, which engage an undercut of the machine that can be driven by the electric motor from behind and thus hold the electric motor on the machine. Compared to securing the electric motor to the machine by screws or bolts, the invention has the advantage that the screws as components are dispensed with, and that there is no need to cut threads. The screwing operation is also dispensed with in the assembly of the electrical unit.
Compared to fastening the electric motor by means of a clamping ring in a circular groove, the invention has the advantage of a simpler and more economical connection of the electric motor to the machine. Another advantage is the tolerance of the connection in the radial direction; the undercut on the machine needs to be made with only relatively little precision with respect to positioning of the electric motor on the machine, and mechanical overdetermination of the fastening of the electric motor to the machine is avoided. The fastening element can be integral, for instance with a housing of the electric motor, so that no separate fastening parts are needed.
The subject of the invention is the reversal of the fastening principle, namely that the machine has one fastening element or a plurality of fastening elements that engage the undercut or a plurality of undercuts of the electric motor from behind.
The subject of the invention sets forth advantageous embodiments and further refinements defined hereinafter.
By the disposition of two or more fastening elements uniformly or nonuniformly around the motor shaft, a uniform fastening of electric motor to the machine relative to the motor shaft or an imaginary motor axis can be attained.
If the fastening element is disposed laterally outside a jacket face of the electric motor, then it is accessible for fastening the electric motor.
The electrical unit is intended in particular as a pump assembly having the electric motor and a piston pump that can be driven by the electric motor and a brake system of a vehicle, and it is used in controlling the pressure in wheel brake cylinders. Depending on the type of brake system, the abbreviations ABS (for anti-lock brake system), TCS (traction control system), ESP (electronic stability program) and EHB (electrohydraulic brake system) are used for such brake systems. In the brake system, the pump assembly serves for instance to return brake fluid from a wheel brake cylinder or a plurality of wheel brake cylinders to a master cylinder (ABS) and/or to pump brake fluid out of a supply container into a wheel brake cylinder or a plurality of wheel brake cylinders (TCS or ESP or EHB). The pump assembly is needed for instance in a brake system with wheel slip control (ABS or TCS) and/or a brake system serving as a steering aid (ESP) and/or an electrohydraulic brake system (EHB). With wheel slip control (ABS or TCS), locking of the wheels of the vehicle during a braking event involving strong pressure on the brake pedal (ABS) and/or spinning of the driven wheels of the vehicle in the event of strong pressure on the gas pedal (TCS) can for instance be prevented. In a brake system serving as a steering aid (ESP), a brake pressure is built up in one or more wheel brake cylinders independently of an actuation of the brake pedal or gas pedal, for instance to prevent the vehicle from breaking out of the track desired by the driver. The pump assembly can also be used in an electrohydraulic brake system (EHB), in which the pump assembly pumps the brake fluid into the wheel brake cylinder or wheel brake cylinders if an electric brake pedal sensor detects an actuation of the brake pedal, or in which the pump assembly is used to fill a reservoir of the brake system.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings.